We propose to investigate the enhancement of tumor induction and/or development previously observed in mice treated with Concanavalin A and challenged with Moloney sarcoma virus, methylcholanthrene, or established tumor cell lines. This will involve comparing the humoral and cellular immune responses of treated versus control animals at various times following challenge with the above oncogenic agents. Spleen cells from control and Con A treated animals will be assayed in 51 chromium release in vitro assays for direct or antibody mediated cellular cytotoxicity against appropriate tumor target cells. Subsequent studies will attempt to elucidate the cell-cell interactions involved in the observed enhancement. It is our hypothesis that treatment with Con A is altering the immune response of the animals by activating subpopulations of suppressor T cells. Extension of these investigations to other lectins known to interact with lymphocyte subpopulations involved in the immune response, and other oncogenic agents will also be done as time and funds permit.